1. Field
The following description relates to technology for canceling interference in a multiple-input multiple-output (MIMO) receiver, which is used, for example, in a multi-cell wireless communication system.
2. Discussion of Related Art
Wireless communication systems are configured to provide a data service in addition to a voice service, and are configured by service providers to suit a multi-cell environment. Examples of the systems include 2nd and 3rd generation mobile communication systems such as CDMA2000, 1xEVDO, and WCDMA, which are based on CDMA, and 3.5th and 4th generation mobile communication systems such as IEEE 802.16, LTE, and LTE-A, which are base on orthogonal frequency-division multiplexing (OFDM).
Signals from an adjacent cell act as interference to a terminal connected to a serving cell when the signals from the adjacent cell have the same frequency as those from the serving cell. Actually, since a 3rd or later generation mobile communication system has a channel bandwidth of several MHz or more, service providers have a limited number of channels such that they often cannot avoid using the same frequency between adjacent cells when systems are established. When there are adjacent cells using the same frequency, a signal transmitted from a base station in one adjacent cell acts as interference to a terminal that is located in a cell boundary, thereby reducing a received signal quality for the other cell (serving cell) and thus causing cell coverage and data rate to be degraded.
In particular, for a heterogeneous network having pico cells and femto cells that are available in an LTE-A system, which is a 4th generation mobile communication, interference between adjacent cells occurs frequently. This causes a macro cell coverage and a reception performance to be degraded.
In order to minimize the interference between cells, a method has been proposed in which allocation of resources to a terminal located in a cell boundary is avoided between a serving base station and an adjacent base station according to a time or frequency axis, thereby enhancing the coverage and data rate in the cell boundary. However, this method has limitations in that an additional system for exchanging resource allocation information between base stations should be established to share the resource allocation information, and spectral efficiency is decreased in a section where resource allocation is avoided between base stations or terminals because all frequency resources are not used.
An existing interference canceller uses a method of finding a covariance matrix for a signal with interference and noise among received signals and its inverse matrix to utilize the inverse matrix as an interference cancellation filter that is applied to the received signals and channel estimates, or a method of assuming that an interference signal is also a received signal and finding a minimum mean square error (MMSE) weight matrix in a higher order than that of multiple-input multiple-output (MIMO) between an original serving base station and a terminal.